Anthropogenic Disturbance.

Direct clearing of vegetation.

Changes in fire frequency.

Soil changes -- plowing, deep chiseling, salinization.

Hydrological changes -- dams, diversions, levees, watertable changes, flood frequency changes.

Atmospheric deposition of nitrogen from pollution.

Displacement of traditional peoples & loss of their land management practices.

Extinction of "keystone" predators, herbivores, etc., leading to community restructuring.

Artificially maintained high herbivore stocking.

Atmospheric deposition of pesticides & industrial pollutants.

Cryptic disturbance often overlooked.